PTL 1 describes a power amplifier used for the power amplification of an RF signal. The power amplifier described in PTL 1 is provided with a plurality of groups each including a first amplification unit and a second amplification unit, and each group is provided with a Doherty combiner. Furthermore, the power amplifier described in PTL 1 is provided with a broadband combiner that combines output signals of each Doherty combiner. In the first amplification unit, a plurality of amplifier circuits that operates in a class AB or a class B is provided in parallel, and a combiner that combines the output signals of these amplifier circuits is further provided. In the second amplification unit, a plurality of amplifier circuits that operates in a class C is provided in parallel, and a combiner that combines the output signals of the amplifier circuits is further provided. In the power amplifier described in PTL 1, each first amplification unit, each second amplification unit, each Doherty combiner, and the broadband combiner are housed in different housings, and the Doherty combiner is easily replaceable.
PTL 2 describes a solidified short-wave band transmission system in a several tens of kW class. The solidified short-wave band transmission system described in PTL 2 includes a combining unit including a plurality of preceding stage combiners and one subsequent stage combiner. Furthermore, a plurality of individually attachable and detachable power amplifiers is provided in each preceding stage combiner. Each preceding stage combiner combines the outputs of the plurality of power amplifiers, and the subsequent stage combiner combines the outputs of the plurality of preceding stage combiners.
PTL 3 describes a configuration in which a plurality of amplification units is arranged between a distributor and a combiner. The amplification unit described in PTL 3 is formed by grouping a plurality of (for example, eight) individual selection amplifiers as one unit. To add an individual selection amplifier, the individual selection amplifier is added in units of the amplification unit.
PTL 4 describes a power combining device including a plurality of band pass filters each having a different pass band and one or a plurality of circulators. In the power combining device described in PTL 4, a first band pass filter and a second band pass filter are connected by a first circulator, and the n-th (n is a natural number) circulator and the n+2 th band pass filter are sequentially connected by the n+1 th circulator.
Furthermore, broadcasters of television broadcasting obtain authorization to do broadcasting business of transmitting television signals in a frequency band, in units of a frequency band obtained by dividing an ultra high frequency (UHF) band (470 to 862 MHz) or a very high frequency (VHF) band (170 to 230 MHz) by a fixed bandwidth. For example, a broadcaster using the UHF band obtains authorization to do broadcasting business in units of a frequency band obtained by dividing the UHF band by a bandwidth of 8 MHz. Note that a bandwidth when the UHF band is divided by country may be 6 MHz or 7 MHz.